It has previously been proposed in U.S. Pat. No. 4,335,763 of McGee et al., issued Jun. 22, 1982, to geometrically rough center the log and clamp the log in a geometrically centered position, to cause charger spindles to engage the ends of the log at the rough center position and to rotate the log about the charger spindles while scanning it with light beams to determine the optimum yield axis of the log. The charger spindles are then moved laterally to align the optimum yield axis of the log at a transfer position which is located at a predetermined position relative to the lathe axis. The log is then moved from the transfer position to the lathe axis by pivoting pendulum arms in engagement with a log. A similar teaching is shown in U.S. Pat. No. 4,398,580 of Sohn et al., issued Aug. 16, 1983.
When scanning the log to determine the optimum yield axis, it is possible to use a break beam type light scanner in which the log is positioned between the light source and the light detector as shown in U.S. Pat. No. 4,335,763 of McGee and U.S. Pat. No. 4,965,734 of Edwards et al., issued Oct. 23, 1990. However, light reflection-type scanning is more accurate and has been used previously in a log charger centering apparatus while rotating the log on the charger spindles during scanning as shown in U.S. Pat. No. 4,884,605 of Ely, issued Dec. 5, 1989.
As shown in U.S. Pat. No. 4,811,776 of Bolton et al., issued Mar. 14, 1989, it is previously been proposed to provide a lathe charger apparatus and method for centering logs by employing two pairs of interconnected rotating disks connected to the ends of the log to provide a pair of double pivots at the opposite ends of the log. However, this is a more complicated log positioning apparatus and includes pendulum arms which are moved laterally along beams, rather than pivoted in order to transfer the log from the charger to the lathe. This prior apparatus of Bolton also employs a geometrical centering step for determining the geometric center axis of the log and then scans the log while rotating it about the charger spindles aligned with the geometric center axis in order to determine the optimum yield axis. The optimum yield axis is aligned with a replicate axis corresponding to the veneer lathe axis by rotating the two pairs of interconnected disks which provide a double axis rotation for adjustment of the spindles. However unlike the present invention, the method used in the Bolton patent does not measure the displacement angle between a common line intersecting two computed centers at the opposite ends of the log and a reference line and does not rotate the log block through the displacement angle to position the common line parallel to a reference line which may be either a vertical axis or the pendulum radius in the manner of the present invention. Finally, there is no movement of the charger spindles along the reference line until the two computed centers coincide at the same point of intersection of the common line with the arc path of travel of pivoted pendulum arms in the manner of the present invention.
The present invention has an advantage over the prior lathe chargers in that it enables the log block to be positioned more accurately so that the charger spindles engaging such log blocks may be closely spaced within a minimum nominal clearance of, for example, 1/8" of the chucks of the pendulum arms when they clamp the log prior to releasing the charger spindles for transferring the log from the charger to the veneer lathe spindles. This enables more reliable transfer of logs to the lathe without dropping the logs and without interference between the pendulum chucks and the charger spindles and/or lathe spindles.